Supersonic Cooling Nozzle Inlet

ABSTRACT

A supersonic cooling system operates by pumping fluid. A geometric element may be situated in a fluid flow path to modify the fluid flow. Because the supersonic cooling system pumps fluid, the cooling system does not require the use of a condenser. The cooling system utilizes a compression wave to facilitate a phase change utilized in a cooling effect. An evaporator operates in the critical flow regime in which the pressure in one or more evaporator nozzles will remain almost constant and then ‘shock up’ to the ambient pressure.

BACKGROUND OF THE INVENTION Description of the Related Invention

Vapor compression systems are used in many cooling applications such as air conditioning and industrial refrigeration. A vapor compression system generally includes a compressor, a condenser, an expansion device, and an evaporator. In a prior art vapor compression system, a gas in a saturated vapor state is compressed to raise the temperature of that gas, the gas then being in a superheated vapor state. The compressed gas is then run through a condenser and turned into a liquid, and heat is rejected from the system. The condensed and liquefied gas is then taken through an expansion device, which drops the pressure and the corresponding temperature. The resulting refrigerant is then boiled in an evaporator, with the refrigerant absorbing heat. The saturated vapor is then returned to the compressor.

FIG. 1 illustrates a vapor compression system 100 as might be found in the prior art. In the prior art vapor compression system 100 of FIG. 1, compressor 110 compresses the gas to (approximately) 238 pounds per square inch (PSI) and a temperature of 190° F. Condenser 120 then liquefies the heated and compressed gas to (approximately) 220 PSI and 117° F. The gas that was liquefied by the condenser 120 is then passed through the expansion valve 130 of FIG. 1. By passing the liquefied gas through expansion value 130, the pressure is dropped to (approximately) 20 PSI.

A corresponding drop in temperature accompanies the drop in pressure, which is reflected as a temperature drop to (approximately) 34° F. in FIG. 1. The refrigerant that results from dropping the pressure and temperature at the expansion value 130 is boiled at evaporator 140. Through boiling of the refrigerant by evaporator 140, a low temperature vapor results. The vapor is illustrated in FIG. 1 as having a temperature of (approximately) 39° F. and a corresponding pressure of 20 PSI.

The cycle carried out by the system 100 of FIG. 1 is an example of a vapor compression cycle. Such a cycle generally results in a coefficient of performance (COP) between 2.4 and 3.5. The COP, as illustrated in FIG. 1, is the evaporator cooling power or capacity divided by compressor power. It should be noted that the temperature and PSI references that are shown in FIG. 1 are exemplary and are for the purpose of illustration only.

FIG. 2 illustrates the performance that might be expected of a vapor compression system similar to that illustrated in FIG. 1. The COP illustrated in FIG. 2 corresponds to a typical home or automotive vapor compression system operating at an ambient temperature of (approximately) 90° F. The COP shown in FIG. 2 corresponds to a vapor compression system utilizing a fixed orifice tube system.

A system like that illustrated in FIG. 1 and FIG. 2 typically operates at an efficiency rate or COP that is far below that of system potential. To compress gas in a conventional vapor compression system like that illustrated in FIG. 1 (system 100) typically takes 1.75-2.50 kilowatts for every 5 kilowatts of cooling power. This exchange rate is less than optimal and directly correlates to the rise in pressure times the volumetric flow rate. Degraded performance is similarly and ultimately related to performance (or lack thereof) by the compressor 110.

Haloalkane refrigerants such as tetrafluoroethane (CH₂FCF₃) are inert gases that are commonly used as refrigerants in refrigerators and automobile air conditioners. Tetrafluoroethane has also been used to cool over-clocked computers. These gases are referred to as R-134 gases. The volume of an R-134 gas can be 600-1000 times greater than its corresponding liquid form. This multiplier shows that the theoretical efficiency of a system utilizing an R-134 gas is much higher than is currently being realized, and evidences the need for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance.

SUMMARY OF THE CLAIMED INVENTION

A first claimed embodiment of the present invention is a supersonic cooling system including a fluid flow path having a high pressure region and a low pressure region. The claimed system includes a pump to facilitate a flow of a fluid through the fluid flow path. The system further includes an evaporator in the fluid flow path. The fluid travels at a velocity that is equal to or greater than the speed of sound in at least a portion of the evaporator. A re-entry ring may be added to the fluid flow path to smooth the flow of the fluid in the system.

A second claimed embodiment of the invention is a method that includes pumping a fluid through a fluid flow path. The fluid flow path includes an evaporator in which the fluid flows at a critical flow rate. The method includes modifying a flow of the fluid with a re-entry ring positioned in the fluid flow path to smooth the flow of the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vapor compression cooling system as may be found in the prior art.

FIG. 2 is a pressure-enthalpy graph for a vapor compression cooling system like that illustrated in FIG. 1.

FIG. 3 is a schematic diagram of an embodiment of a supersonic cooling system.

FIG. 4 is a pressure-enthalpy graph for a supersonic cooling system like that illustrated in FIG. 3.

FIG. 5 is a sectional view illustrating the converging portion of a nozzle with an exemplary inlet that may be used in a supersonic cooling system.

FIG. 5A is a detail view of a nozzle throat inlet like that shown in FIG. 5.

FIG. 6 is a sectional view illustrating the converging portion of an alternative embodiment of a nozzle with a re-entry ring.

FIG. 6A is a detail view of the nozzle throat inlet illustrated in FIG. 6.

FIG. 7 is a sectional view illustrating the converging portion of another exemplary nozzle with an enlarged re-entry ring.

FIG. 7A is a detail view of the nozzle throat inlet illustrated in FIG. 7.

FIG. 8 is a sectional view illustrating the converging portion of another exemplary nozzle that includes a re-entry ring with a convex surface that arcs continuously from the aperture to the wall of the inlet body.

FIG. 8A is a detail view of the nozzle throat inlet illustrated in FIG. 8.

FIG. 9 is a sectional view illustrating the converging portion of another exemplary nozzle with a profile that includes both a convex arc and a concave arc.

FIG. 9A is a detail view of the nozzle throat inlet illustrated in FIG. 9.

FIG. 10 is a sectional view illustrating a nozzle throat inlet having a convex arc and a concave arc and forming an extended approach.

FIG. 11 is a sectional view illustrating a nozzle throat inlet with an elongated tapered section.

FIG. 12 is a sectional view illustrating a nozzle throat inlet with an elongated tapered section and a recirculation ring.

FIG. 13 is a sectional view illustrating a nozzle throat inlet with a first converging area and a second converging area.

FIG. 14 is a sectional view illustrating a nozzle throat inlet with a multi-tiered converging area.

FIG. 15 is a sectional view illustrating a nozzle throat inlet with an extended approach.

FIG. 16 is a sectional view illustrating a nozzle throat inlet with a further extended approach.

FIG. 17 is a sectional view illustrating a nozzle throat inlet with a cylindrical converging section.

FIG. 18 is a sectional view illustrating a nozzle throat inlet with an arced converging section and an extended approach.

FIG. 19 is a sectional view illustrating a nozzle throat inlet with a stepped and tapered converging area.

FIG. 20 is a sectional view illustrating another nozzle throat inlet with a stepped and tapered converging area.

FIG. 21 is a sectional view illustrating a nozzle throat inlet with a stepped cylindrical converging area.

FIG. 22 is a sectional view illustrating a nozzle throat inlet with a stepped and tapered converging area.

FIG. 23 is a sectional view illustrating a nozzle throat inlet with a tapered converging section and a step leading to an extended approach.

FIG. 24 is a sectional view illustrating another nozzle throat inlet with a tapered converging section and a step leading to an extended approach.

FIG. 25 is a sectional view illustrating another nozzle throat inlet with a tapered converging section and a step leading to an extended approach.

FIG. 26 is a sectional view illustrating a nozzle throat inlet with a tapered converging section and a step leading to an extended approach in which the converging section includes a conical insert.

FIG. 27 is a sectional view illustrating a nozzle throat inlet with a porous media section.

FIG. 28 is a sectional view illustrating a nozzle throat inlet with an arced converging section and a re-entry ring.

FIG. 29 is a sectional view illustrating another nozzle throat inlet with a first converging area and a second converging area.

FIG. 30 is a sectional view illustrating another nozzle throat inlet with a first converging area and a second converging area.

FIG. 31 is a sectional view illustrating a nozzle throat inlet with an arced converging area and a pair of recirculation rings.

FIG. 32 is a sectional view illustrating a nozzle throat inlet with an arced converging area and a straight-walled recirculation ring.

FIG. 33 is a graph illustrating the change of pressure over axial position of selected configurations of the converging-diverging nozzle throat inlet.

FIG. 34 illustrates an exemplary conformation of the converging and throat section of a converging-diverging nozzle.

FIG. 35 illustrates the converging and throat section of a nozzle with a shortened tapered portion.

FIG. 36 illustrates the converging and throat section of a nozzle with a further shortened tapered portion.

FIG. 37 illustrates the converging and throat section of a nozzle with a still further shortened tapered portion.

FIG. 38 illustrates a method of operation for a cooling system utilizing a supersonic cooling cycle.

DETAILED DESCRIPTION

FIG. 3 illustrates an exemplary cooling system 300 utilizing a supersonic cooling cycle in accordance with an embodiment of the present invention. While generally described as a cooling system herein, it will be recognized by those skilled in the art that the system may also be installed in a heat pump configuration, and heat a given area with transferred heat.

The cooling system 300 does not need to compress a gas as otherwise occurs at compressor 110 in the prior art vapor compression system 100 illustrated in FIG. 1. Cooling system 300 operates by pumping liquid. Because cooling system 300 pumps liquid, the compression cooling system 300 does not require the use of a condenser 120 as does the prior art compression system 100. Compression cooling system 300 instead utilizes a compression wave. The evaporator of cooling system 300 operates in the critical flow regime where the pressure in the evaporator will remain almost constant and then ‘jump’ or ‘shock up’ to the ambient pressure.

The cooling system 300 of FIG. 3 recognizes a heightened degree of efficiency in that the small pump 310 of the system 300 is not required to draw as much power as the compressor 110 in a prior art compression system 100 like that illustrated in FIG. 1. A supersonic compression cooling system designed according to an embodiment of the presently disclosed invention may recognize exponential performance efficiencies. For example, a prior art compression system 100 as illustrated in FIG. 1 may require 1.75-2.5 kilowatts to generate 5 kilowatts of cooling power. Prior art compression system 100 therefore may operate at a coefficient of performance (COP) of less than 3. A system 300 like that illustrated in FIG. 3 may pump fluid from approximately 14.7 to approximately 120 PSI with the pump drawing power at approximately 500 W (0.5 kilowatts), and with the system 300 generating 5 kilowatts of cooling power. The system 300 may therefore operate with a COP of 3 or greater, or 4 or greater, or 5 or greater, or 6 or greater, or 7 or greater, or 8 or greater, or 9 or greater, or 10 or greater, or 20 or greater, or 30 or greater, or 40 or greater, or 50 or greater. As a result of the cycle illustrated in FIG. 3, and the resultant increased efficiencies, system 300 may utilize many working fluids, including but not limited to water.

Pump 310 establishes circulation of a compressible working fluid through a fluid flow path of system 300. Pump 310 may circulate the working fluid throughout system 300 through the use of vortex flow rings. Vortex rings operate as energy reservoirs whereby added energy is stored in the vortex ring. The progressive introduction of energy to a vortex ring via pump 310 causes the corresponding ring vortex to function at a level such that energy lost through dissipation corresponds to energy being input.

Pump 310 operates to raise the pressure of a liquid being used by system 300 as a working fluid from, for example, 20 PSI to 100 PSI or more. Some systems may operate at an increased pressure of approximately 300 PSI. Other systems may operate at an increased pressure of approximately 500 PSI. Fluid temperature at the pump inlet may be approximately 95 F.

An evaporator of supersonic cooling system 300 may include at least one evaporator tube or nozzle 320. The evaporator nozzle 320 may be constructed with a converging-diverging configuration. A ‘converging-diverging’ configuration is generally representative of a nozzle design that includes an inlet, throat, and exit with a continuous flow path in fluid communication with each section. The inlet section receives a fluid, which is ultimately expelled at the exit portion. The diameter of the flow path decreases (i.e., converges) from the inlet portion to the throat portion of the nozzle. The nozzle 320 may include a geometric element, such as a specific tapering pattern or a re-entry ring, upstream of the throat to modify the fluid flow. The nozzle then expands (i.e., diverges) from the throat to the exit portion of the nozzle.

As the working fluid is introduced to the evaporator nozzle 320, the evaporator nozzle 320 induces a pressure drop e.g., to less than 20 PSI, or less than 10 PSI, or to approximately 5.5 PSI. The pressure drop establishes a low pressure region and a concurrent phase change that result in a lowered temperature. The evaporator nozzle 320 of system 300 operates in the critical flow regime of the working fluid, thereby establishing a compression wave that assists in the acceleration of the working fluid.

The evaporator nozzle 320 may also induce cavitation in the working fluid as part of the phase change. The cavitation serves to reduce the speed of sound in the working fluid. As the working fluid is accelerated and undergoes a pressure drop and phase change, the working fluid further ‘boils off’ in evaporator nozzle 320, providing the desired cooling effect in the system 300. In embodiments in which the working fluid is water, the water may be cooled to 35-45° F., or approximately 37° F. At or near the exit of the evaporator nozzle 320, the working fluid ‘shocks up’ to approximately 20 PSI.

To facilitate the dissipation of heat in the system 300, the evaporator nozzle 320 may be coupled with a heat exchanger 330. The heat exchanger 330 may be thermally coupled to a coolant fluid used in the system 300, with the coolant fluid being circulated around or through an area or an object to be cooled. The working fluid of the system 300 may be at a temperature of approximately 90-100° F. at the inlet of the pump 310.

As noted above, the evaporator nozzle 320 includes an inlet portion 340, a throat portion 350, and an expansion (exit) portion 360. The inlet portion 340 receives the working fluid from an inlet section of the cooling system 300. The working fluid is directed into the throat portion 350 of the nozzle 320. The throat portion 350 provides a duct of substantially constant profile (normally circular) through which the working fluid is forced. The expansion (exit) portion 360 provides an expanding tube-like member wherein the diameter of the fluid flow path progressively increases between the throat portion 350 and the outlet of the expansion portion 360. The actual profile of the expansion portion 360 may depend upon the specific working fluid to be used in the system 300. As discussed below with reference to FIGS. 5-13, the profile of various segments of the evaporator nozzle 320 may be modified to alter the operating characteristics of the cooling effect of a given working fluid in a specific application. Operating conditions of an exemplary supersonic cooling system 300 utilizing an evaporator nozzle 320 may be seen in FIG. 4, a pressure-enthalpy diagram showing an exemplary performance curve.

During the operation of the evaporator nozzle 320, when the working fluid enters the throat portion 350, the fluid is choked. The working fluid is then accelerated to high (supersonic) speed as it flows through the expansion portion 360. The inlet pressure and the diameter of the throat orifice may be selected so that the speed of the working fluid at the entry of the throat portion 350 is approximately the speed of sound (Mach 1).

As the working fluid travels through the evaporator nozzle 320, the acceleration of the working fluid causes a sudden drop in pressure which results in cavitation that commences at the boundary between the exit of the inlet portion 340 and the entry to the throat portion 350. Cavitation is also triggered along the wall of the throat portion 350. Cavitation results in bubbles of the working fluid in the vapor phase being present within the fluid in the liquid phase, thereby providing a multi-phase working fluid. The creation of such vapor bubbles requires the input of energy for the input of latent heat of vaporization and as a result the temperature falls. At the same time, the reduction in pressure together with the working fluid achieving a multi-phase state causes the local speed of sound in the working fluid to be lowered, with the result that the working fluid exits the throat portion 350 at a supersonic speed of, for example, Mach 1.1 or higher. It is noted that the reduction in the localized speed of sound changes the character of the flow from traditional incompressible flow to a regime more in character with high speed nozzle flow.

As the working fluid travels within the expansion portion 360, the pressure remains at a low level and the fluid expands. As a result of the expansion, the flow accelerates further, reaching a speed on the order of for example approximately Mach 3. As the fluid accelerates and pressure is reduced, the local static pressure drops, so that more vapor is generated from the surrounding liquid working fluid. As the working fluid moves below the saturation line, the cooling effect required for the cooling system 300 is generated and the flow behaves as if it was in an over-expanded jet. Once the working fluid has picked up sufficient heat, and due to frictional losses, the fluid shocks back to a subsonic condition and returns to ambient conditions.

One factor that affects the cooling power of the cooling system 300 is the change in pressure over time (dp/dt) as the working fluid is introduced to the inlet of the throat 350 of the evaporator nozzle 320. It may be desirable to maximize the pressure drop to the lowest pressure possible at which nucleation is avoided, the lowered pressure driving the fluid flow into the metastable region. Driving the flow of the working fluid into the metastable region may ultimately reduce the pressure in downstream sections of the nozzle 320, thereby further reducing the temperature of the fluid.

The evaporator nozzle 320 may typically be a converging-diverging nozzle. As illustrated by the following exemplary configurations, many geometric conformations, and modifications to the basic conformations, of the converging-diverging nozzle may be employed.

FIG. 5 illustrates an exemplary inlet 500 to the throat 350 of the nozzle 320. The converging section 520 of the inlet body 510 may be conical, cylindrical, planar, or annular in shape immediately upstream of the throat 350. The inlet 500 may accelerate the flow of the working fluid as it passes through the inlet aperture 540 and enters the throat 350 of the evaporator nozzle 320. As shown in further detail in FIG. 5A, a flange 530 in which aperture 540 is formed may have a flat upstream surface.

FIG. 6 illustrates the inlet 500 with a re-entry ring 650 added to the upstream side of the inlet aperture 540. The introduction of the re-entry ring 650 into the fluid flow path “smoothes” the flow, thereby reducing any adverse flow irregularities, which may lead to an increased pressure drop and attendant reduced temperature. As shown in further detail in FIG. 6A, the re-entry ring 650 may be a protrusion shaped as a raised annular element surrounding the inlet aperture 540.

As illustrated in FIG. 7, the smoothing effect may be increased by adding an enlarged, with respect to re-entry ring 650, re-entry ring 750. As shown in further detail in FIG. 7A, the re-entry ring 750 has the same general conformation as re-entry ring 650, but includes a larger raised portion.

FIGS. 8 and 9 illustrate a further progression of modification to the re-entry ring that may create increasing flow-smoothing effects. As is illustrated in FIGS. 8 and 9, the conformations referred to herein as re-entry rings in many cases may simply be the profile of the interior of the converging section of the nozzle leading to the inlet aperture. FIG. 8 shows a re-entry ring 850 that includes a convex surface that arcs continuously from the aperture 540 to the wall of the inlet body 510. FIG. 8A is a detail view of the throat area of the nozzle illustrated in FIG. 8.

FIG. 9 illustrates still another possible conformation of a re-entry ring 950. Re-entry ring 950 includes a profile that begins with a convex arc. As is illustrated in further detail in FIG. 9A, the convex arc extends from the inlet aperture 540 to a middle section of the re-entry ring 950. The profile of the re-entry ring 950 then continues as a concave arc to the wall of the inlet body 510. The term “convex/concave profile” refers to a reentry ring 950 having such profile.

FIG. 10 illustrates a nozzle throat inlet 500 with an extended re-entry ring 1050. The shoulders of the re-entry ring 1050 are extended into the converging section 520 so that the shoulders form an extended approach 1060 to the inlet aperture 540.

FIG. 11 shows a nozzle throat inlet in which the re-entry ring 1150 extends for substantially the length of the converging section 520. The re-entry ring 1150 extends away from the inlet aperture 540 to form an extended approach 1160. The re-entry ring then gently tapers to the beginning of the converging section 520.

FIG. 12 illustrates a nozzle throat inlet 500 with a profile similar to that of the nozzle shown in FIG. 11. A re-entry ring 1250 may include a recirculation ring 1270 to further modify the flow of the fluid in the inlet 500.

FIG. 13 illustrates an inlet 500 with a re-entry ring 1350 that is shaped to form a first converging section 1380 and a second converging section 1390.

FIG. 14 shows an inlet 500 with a re-entry ring 1450 that forms a multi-tiered converging section 520. The re-entry ring 1450 may include one or more tapered shoulders 1460 that rapidly reduce the diameter of the converging section 520.

FIG. 15 shows an inlet 500 that may include a basic tapered re-entry ring 1550. However, in FIG. 15, the re-entry ring 1550 extends into the converging section 520 to form an extended approach 1560 to the inlet aperture 540.

FIG. 16 shows an inlet 500 that includes a basic tapered re-entry ring 1650 further extend to form a further extended approach 1660 to the inlet aperture 540 as compared to extended approach 1560.

FIG. 17 illustrates an inlet 500 that is cylindrical until reaching the re-entry ring 1750. The profile of the inlet 500 is similar to that shown in FIG. 6, but with and extended approach 1760 to the inlet aperture 540.

FIG. 18 illustrates an inlet 500 with an extended approach 1860. The re-entry ring 1850 includes a step 1870 at the transition of the converging section 520 to the approach 1860 to the inlet aperture 540.

FIG. 19 shows an inlet 500 also with an extended approach 1960 to the inlet aperture 540. One or more steps 1970 are included in the re-entry ring 1950. The inlet 500 has a tapered converging section 520 that reduces in diameter in the direction of fluid flow.

FIG. 20 illustrates an inlet 500 with a construction similar to that shown in FIG. 19. The inlet 500 illustrated in FIG. 20 also includes a re-entry ring 2050 with steps 2070 upstream of an extended approach 2060. The steps 2070 are spaced further apart as compared to the steps 1970, and therefore form an elongated central section 2080.

FIG. 21 illustrates an inlet 500 with an extended re-entry ring 2150 that forms an extended approach 2160. A large step 2170 forms a transition section 2180 in the converging section 520. An upstream portion of the converging section 520 is cylindrical.

FIG. 22 illustrates an inlet 500 with an extended re-entry ring 2250 that forms an extended approach 2260. A step 2170 is included between the upstream portion of the converging section 520 and a transition section 2280. The upstream portion of the converging section 520 tapers inward to the step 2170.

FIGS. 23-25 show a series of similarly configured inlets 500. FIG. 23 illustrates an inlet 500 with an extended re-entry ring 2350 forming an extended approach 2360. The converging section 520 tapers inward to a small step 2370. In FIG. 24, the re-entry ring 2450 includes a medium step 2470 at the mouth of the approach 2460. FIG. 25 includes a re-entry ring 2550 with a large step 2570 at the approach 2560. The difference in the inlets 500 illustrated in FIGS. 23-25 is the increasing size of the steps 2370, 2470, 2570. The increasing size of the steps 2370, 2470, 2570 leads to a slightly less sharply angled upstream section of the tapered converging section 520.

FIG. 26 shows a variation on the theme of the inlets illustrated in FIGS. 23-25. The inlet 500 retains an extended re-entry ring 2650 that forms a tapered converging section 520 with a step 2670 leading to an extended approach 2660. A conical element 2680 may be positioned in a central area of the converging section 520. The conical element 2680 creates an annular flow pattern in the converging section 520.

FIG. 27 illustrates an inlet 500 with a partially extended re-entry ring 2750 that forms a converging section 520 with a tapered downstream portion with a step 2770 leading to an extended approach 2760. A section of porous media 2780 may be included in the converging section 520 to further modify and smooth the flow of fluid. The porous media 2780 may reduce the local static pressure.

FIG. 28 illustrates an inlet 500 with an extended re-entry ring 2850. The re-entry ring 2850 includes a raised portion at the inlet to an extended approach 2860. The extended re-entry ring 2850 forms a converging section 520 with arced walls that narrow to the inlet of the approach 2860.

FIG. 29 shows an inlet 500 with an extended re-entry ring 2950 that includes a step 2970 leading to an extended approach 2960. The converging section 520 arcs inward to a narrow section midway in the inlet 500. A slight expansion then leads to an expanded section 2980 just upstream of the step 2970.

FIG. 30 illustrates an inlet 500 with a profile similar to that of the inlet 500 depicted in FIG. 29. In FIG. 30, the extended approach 3060 is slightly longer than approach 2960.

FIG. 31 illustrates an inlet 500 with a profile similar to that shown in FIG. 18. However, instead of utilizing a step 1870 to the approach 3160, the re-entry ring 3050 includes two recirculation rings 3170. It will be recognized by those skilled in the art that any number of recirculation rings may be employed according to the conditions of a given installation. FIG. 32 shows an inlet 500 with a profile similar to that of FIG. 31. However, in the inlet 500 of FIG. 32, a straight-sided recirculation ring 3270 is utilized. Various profiles, including but not limited to steps of other straight edged profiles, may be utilized for the recirculation rings.

FIG. 33 is a graph showing pressure (Y-axis) relative to the axial position in the nozzle (X-axis). The graph illustrates that the various flow altering elements; specifically including but not limited to re-entry rings, recirculation rings, steps, and shoulders; may affect the position at which the pressure change occurs, and magnitude of the pressure changes brought about in the evaporation nozzle 320.

It will be recognized by those skilled in the art that various other flow altering elements with profiles not illustrated herein may be positioned upstream of the inlet aperture 540 to affect the flow pattern of the nozzle. Specific profiles of the flow altering elements may be determined by the working fluid chosen and the operating conditions in which the cooling system 300 is implemented.

A phenomenon that may yield enhanced temperature reduction in the supersonic cooling system 300 is a reduction in pressure upstream of the throat 350. Lowering the upstream pressure may cause the pressure to remain close to the saturation pressure to achieve lower subcooling of the working fluid. Lowered subcooling may increase the time that the fluid flow is in the metastable region.

In addition to the configurations discussed above, various conformations of the evaporator 320 may be utilized to achieve this lowered pressure effect. FIGS. 34-37 illustrate a variety of such profiles. FIGS. 34-37 show that the length of the tapered portion of the converging section 340 may be varied to modify the fluid flow within the converging section 340. FIGS. 34-37 also illustrate conformations with a tapered portion of decreasing length, and with a generally flat interface to the throat 350. It will be recognized by those skilled in the art that the taper of the converging section 340 as well as the length of the tapered portion may be varied according to the characteristics of a given implementation and the working fluid chosen.

FIG. 38 illustrates a method of operation 3800 for the cooling cycle utilized in the systems disclosed herein. In step 3810, a pump raises the pressure of a liquid. The pressure may, for example, be raised from 20 PSI to in excess of 100 PSI. As mentioned above, the increased pressure may be 300 PSI or even 500 PSI. In step 3820, fluid flows through the nozzle/evaporator tube(s). Pressure drop and phase change as the fluid accelerates through the evaporator result in a lower temperature as fluid is boiled off in step 3830.

Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime. Critical flow occurs when the velocity of the fluid is equal to or greater than the speed of sound in the fluid. In critical flow, the pressure in the channel will not be influenced by the exit pressure and at or near the channel exit, the fluid will “shock up” to the ambient condition. In critical flow the fluid will also stay at the low pressure and temperature corresponding to the saturation pressures. In step 3840, upon the fluid exiting the evaporator tube, the fluid “shocks up” to 20 PSI. A heat exchanger may be used in optional step 3850. Cooling may also occur via convection on the surface of the housings of the cooling systems that utilize the supersonic cooling cycle.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. 

1. A supersonic cooling system, comprising: a pump to facilitate a flow of a fluid through a fluid flow path having both a high pressure region and a low pressure region; and an evaporator in the fluid flow path, wherein the evaporator accelerates the fluid to a velocity that is equal to or greater than the speed of sound, the evaporator including at least one evaporator nozzle with a geometric element situated upstream of an inlet to a throat of the at least one evaporator nozzle, the geometric element affecting a flow of fluid within the evaporator.
 2. The supersonic cooling system of claim 1, wherein the geometric element is a tapered inlet section that reduces the pressure of the fluid.
 3. The supersonic cooling system of claim 1, wherein the geometric element is a re-entry ring including a protrusion on a surface of a flange that includes an aperture leading to the throat, the re-entry ring reducing adverse flow irregularities in a flow of fluid entering the throat.
 4. The supersonic cooling system of claim 2, wherein the re-entry ring includes a convex surface with an arc beginning at a surface of a flange including an aperture leading to the throat and continuing to an upstream point on an inlet body wall, the convex surface providing the re-entry ring with increased surface area to reduce adverse flow irregularities in a flow of fluid entering the throat.
 5. The supersonic cooling system of claim 2, wherein the re-entry ring has a convex/concave profile that provides the re-entry ring with increased surface area to reduce adverse flow irregularities in a flow of fluid entering the throat.
 6. The supersonic cooling system of claim 2, wherein the re-entry ring includes a profile having a convex arc beginning at a surface of a flange including an aperture leading to the throat and continuing to a middle section of the re-entry ring, the curvature of the profile continuing as a concave arc to an upstream point on an inlet body wall, the profile of the re-entry ring providing an increased surface area to reduce adverse flow irregularities in a flow of fluid entering the throat.
 7. The supersonic cooling system of claim 1, wherein the evaporator is located in the low pressure region of the fluid flow path, and the evaporator facilitates a phase change of the fluid.
 8. The supersonic cooling system of claim 1, wherein the evaporator accelerates the fluid to a critical flow regime of the fluid.
 9. The supersonic cooling system of claim 1, wherein the evaporator maintains a substantially constant pressure in the fluid as the fluid flows through the fluid flow path in the evaporator.
 10. A supersonic cooling method, comprising: pumping a fluid through a fluid flow path, the fluid flow path including an evaporator wherein the fluid flows at a critical flow rate; and modifying a flow of the fluid with a geometric element positioned in the fluid flow path to modify the fluid flow in the evaporator.
 11. The supersonic cooling method of claim 10, wherein the modification of the flow of the fluid occurs as a result of a tapering of an inlet section upstream of a flange defining an aperture leading to a throat of an evaporator nozzle at the evaporator, the tapering lowering the pressure of the fluid.
 12. The supersonic cooling method of claim 10, wherein the modification of the flow of the fluid occurs as a result of the re-entry ring being positioned on an upstream surface of a flange defining an aperture leading to a throat of an evaporator nozzle at the evaporator, the re-entry ring reducing adverse flow irregularities in the fluid flow.
 13. The supersonic cooling method of claim 10, wherein the modification of the flow of the fluid occurs as a result of an expanding arc of the re-entry ring that increases a flow modifying surface area.
 14. The supersonic cooling method of claim 10, further comprising accelerating the fluid in the evaporator to induce a phase change of the fluid.
 15. The supersonic cooling method of claim 10, wherein the acceleration of the fluid at the evaporator is to a velocity equal to or greater than the speed of sound in the fluid.
 16. The supersonic cooling method of claim 10, further comprising transferring heat to the fluid via a heat exchanger thermally coupled to the fluid flow path.
 17. The supersonic cooling method of claim 10, wherein the flow of the fluid is modified to include vortex ring formation.
 18. The supersonic cooling method of claim 10, further comprising reducing pressure in the evaporator to less than 20 PSI.
 19. A cooling system, comprising: an evaporator having an evaporator nozzle with a re-entry ring, the re-entry ring situated upstream of an inlet to a throat of the evaporator nozzle, the evaporator accelerating a fluid to a velocity that is greater than or equal to the speed of sound, the re-entry ring reducing adverse flow irregularities in a flow of fluid within the evaporator.
 20. The cooling system of claim 19, further comprising a pump upstream of the evaporator, the pump facilitating a flow of a fluid through a fluid flow path having a high pressure region and a low pressure region. 